The present invention discloses a hand-held cutting device of that type generally employed in use applications such as carton opening and the like, wherein said device of the instant invention is provided with a new and improved blade guard means, the combined mechanical features thereof being hereinafter referred to and defined as a "safety utility knife", the same of which is more specifically comprised of a shaped handle having a replaceable blade statically positioned and secured therein, said blade being mechanically cooperative with a compression-extension spiral spring loaded blade guard in such a manner whereby after manually operable trigger depression of a compression-extension spiral spring loaded blade guard release means there is in turn enabled spring compression retraction of said blade guard into said handle upon use application of said knife, thereby exposing said blade for cutting operation, wherein said blade guard thereafter automatically extends upon completion of use application and safety locks upon manual trigger release by way of extension of the multiply acting compressed spiral spring forces aforementioned, to thereby mechanically cause said blade guard to assume a non-use safety configuration position relative to said blade.
In general, the prior art hand-held safety utility knife cutting device disclosures are comprised of the following major types. First, being those similar in some respects to the instant invention by virtue of having a shaped handle means provided with a statically positioned and retained cutting blade assembled therein, in the first instance having blade guard means being manually operable from an extended safe configuration to a retracted blade exposed working position as exemplified by that safety utility knife taught in U.S. Pat. No. 2,784,489 to Reise, dated Mar. 12, 1957. Or, in the second instance, as taught in U.S. Pat. No. 2,644,230 to Anderson, dated July 7, 1953, disclosing a hand-held safety utility knife provided with a trigger released retractable blade guard operable by the embodiment of a modified torsion spring means.
A second general type of hand-held safety utility knife cutting device disclosure, embodying the incorporation of spring means, is exemplified by that as taught in U.S. Pat. No. 2,743,523 to Honey, dated May 1, 1956, wherein the blade guard per se is comprised of a shaped deformable band spring provided with a slotted opening through which one corner of the cutting blade projects when pressure is applied to the knife to cause cutting of the surface to be severed.
A third general type of hand-held safety utility knife cutting device having spring activated blade guard means is also taught, exemplary of which would be those such as respectively shown in U.S. Pat. No. 1,222,366 to Curry, dated Apr. 10, 1917, U.S. Pat. No. 2,376,887 to Walters, dated May 29, 1945, and U.S. Pat. No. 2,730,800 to Bailey, dated Jan. 17, 1956, wherein the protective blade guard means are all operable from a safe blade encasing to a retracted blade exposed working position by overcoming the resistive force of a torsion spring means when use application pressure is imparted to the knife to cause cutting of the surface to be severed.
Collaterally, compression-extension spiral spring loaded blade guards for cutting devices other than those which would be classed as safety utility knives are also disclosed by certain prior art teachings, exemplary among those of which would be U.S. Pat. No. 390,759 to DeLamarre, dated Oct. 9, 1888, wherein an oyster knife is provided with a compression-extension spiral spring loaded blade end guard assembled to two detented rod guides and having user rotatable ring means on the knife handle thereof to lock said blade end guard in a spring compressed retracted position and afterwards release it therefrom. The disclosure set forth in U.S. Pat. No. 1,181,681 to Nicaud, dated May 2, 1916, teaches a dagger having a cylindrical pointed-rod type blade being provided with a compression-extension spiral spring loaded tubular sheath which retracts annularly into the handle of said dagger upon use impact compression of said spring and extends to the safe blade encasing position upon release, while in U.S. Pat. No. 2,512,237 to Mravik, dated June 20, 1950, there is taught a similar compression-extension spiral spring loaded annularly retractable blade sheath for a pocket pen type of knife. In. U.S. Pat. No. 2,882,598 to Fidelman, dated Apr. 21, 1959, there is disclosed a compression-extension spiral spring loaded telescopic sleeve comprising a combined blade guard and work guide means for an envelope opener.
It should be understood that some of the features of the instant invention have, in some respects, certain structural and functional similarities to teachings separately set forth in the prior art disclosures heretofore cited and briefly discussed. However, as will hereinafter be pointed out, the instant invention is distinguishable from said earlier inventions in one or more ways in that the present invention has utility features and new and useful advantages, applications, and improvements in the art of safety utility knives not heretofore known.